This invention relates to a fossil-fired thermal system such as a power plant or steam generator, and, more particularly, to a method for determining correction factors to a set of xe2x80x9cChoice Operating Parametersxe2x80x9d, including effluent concentrations, such that combustion stoichiometric consistency and thermodynamic conservations of the system are both achieved. Correcting Choice Operating Parameters is accomplished through multidimensional minimization techniques operating on xe2x80x9cSystem Effect Parametersxe2x80x9d which are reflective of the system at large including system heat rate. The corrected Choice Operating Parameter may then be supplied to Input/Loss methods as used to determine fuel chemistry, heating value, fuel flow and other parameters for the monitoring and improvement of system heat rate.
The importance of accurately determining system heat rate is critical to any thermal system (heat rate being inversely related to system thermal efficiency, common units of measure for heat rate are Btu/hour per kilowatt, or Btu/kWh). If practical hour-by-hour reductions in heat rate are to be made, and/or problems in thermally degraded equipment are to be found and corrected, then accuracy in determining system heat rate is a necessity. Accurate system heat rates using xe2x80x9cInput/Loss methodsxe2x80x9d are achievable given input data with no discernable error. Specifically, xe2x80x9cThe Input/Loss Methodxe2x80x9d and its associated technologies are described in the following U.S. patent applications: Ser. No. 09/273,711 (hereinafter termed ""711), Ser. No. 09/630,853 (hereinafter termed ""853), Ser. No. 09/827,956 (hereinafter termed ""956), and Ser. No. 09/971,527 (hereinafter termed ""527); and in their related provisional patent applications and Continuation-In-Parts. Rudimentary Input/Loss methods are described in U.S. Pat. No. 5,367,470 issued Nov. 22, 1994 (hereinafter termed ""470), and in U.S. Pat. No. 5,790,420 issued Aug. 4, 1998 (hereinafter termed ""420). In addition to The Input/Loss Method as described in ""711, the subject of the present invention relates to any method which uses measurements of effluent concentrations, typically CO2 and O2, and other non-flow xe2x80x9cOperating Parametersxe2x80x9d, and when using this data determines one or more of the following: fuel flow, effluent flow, emission rates, fuel chemistry, fuel heating value, boiler efficiency, and/or system heat rate. Meanings of terms specific to this invention and delineated by quote marks are defined below.
Two highly sensitive inputs to Input/Loss methods are the CO2 and H2O effluent concentrations as measured, or as otherwise determined, at the boundary of the system. There are other sensitive inputs such as effluent O2. The importance of accurately measuring effluent concentrations and Operating Parameters has been discussed by the present inventor in his U.S. patents and applications cited herein. His works have stressed the importance of such measurement accuracy, especially when monitoring a power plant in real-time, for making essentially continuous improvements. Such concern for measuring effluents in a direct manner, as required by ""470 and ""420, resulted in the invention of a high accuracy infrared instrument described in U.S. Pat. No. 5,327,356, whose technology was supported when applied to coal-fired systems by U.S. Pat. No. 5,306,209.
The invention of ""470 is noteworthy as background for this invention for it teaches to repetitively adjust, or iterate, on xe2x80x9can assumed water concentration in the fuel until consistency is obtained between the measured CO2 and H2O effluents and those determined by stoichiometrics based on the chemical concentration of the fuelxe2x80x9d. Some aspects of ""470 are dependent upon high accuracy directly measured CO2 and H2O effluent concentrations. The difficulty is that high accuracy measurements may not be possible. Another difficulty with the details of ""470 lies with the fact that adjusting fuel water as taught in ""470, which alters the computed effluent water, has no prima facie effect on a dry-base effluent CO2. It is true, for example, that if fuel water is increased, the relative fraction of the other fuel""s constituents, per mole of total As-Fired fuel, will decrease assuming that the fuel""s other constituents, nitrogen, oxygen, carbon, hydrogen, sulfur and ash, remain proportionally constant to each other. However, it would be unusual that any given fuel water adjustment would produce an exactly consistent effluent CO2 and O2; with the exception where the dry chemistry is constant. Further, if the fuel has a variable ash content, ash having a pure dilutive or concentrative influence on fuel chemistry and fuel heating value, then such a variable effect could not possibly be determined by merely iterating on fuel water. A higher assumed fuel water may decrease a wet-base effluent CO2, but the actual fuel could contain much lower ash, thus actually increasing the amount of fuel carbon relative to the whole. The approach of simple water iterations of the ""470 patent is useful in certain situations, such as where the coal fuel bears little and constant ash, and, further, where high accuracy and consistent effluent CO2 and H2O measurements are made. However, ""470 has limitations given a lack of technology in assuring consistency in combustion stoichiometrics and for relying on high accuracy effluent measurements.
The invention of ""420 extends the approach of ""470 to include combustion turbine systems. The ""420 patent is concerned with methods for improving heat rate, determining effluent flows and determining fuel flow of fossil-fired systems through an understanding of the total fuel energy flow (fuel flow rate times heating value). ""420 explains that the molar quantity of fuel water xe2x80x9cis iterated until convergence is achievedxe2x80x9d; i.e., using direct, unaltered, effluent measurements resulting in an As-Fired heating value and fuel flow rate. Again, as water is altered, the aggregate of all other fuel constituents are altered in opposite fashion to maintain a normalized unity moles of fuel. As with the approach of ""470, ""420 requires high accuracy instrumentation, stating xe2x80x9cthe apparatus necessary for practicing the present invention includes utilization of any measurement device which may determine the effluent concentrations of H2O and CO2 to high accuracyxe2x80x9d. When considering direct effluent measurements required for Input/Loss methods, such as effluent concentrations of CO2, O2, and other Operating Parameters, measurement errors rarely cancel and no single instrument has perfect accuracy.
The problem which is not addressed by ""470 or ""420 Input/Loss methods is that great sensitivity may exist between an effluent concentration measurement and a parameter which effects system heat rate. This is best illustrated by the sensitivity effluent CO2 has on a computed heating value: a 1.0% xcex94molar/molar change in CO2 will produce a 2.7% change in heating value for a typical Powder River Basin coal. This typically implies 270 xcex94Btu/kWh in heat rate, which may be worth at least $5 million/year in fuel costs for a 600 Mwe coal-fired system. Further, it is the nature of power plant stoichiometrics that essentially any selection of Choice Operating Parameters have inter-dependencies. A 1.0% change in CO2 may be easily caused by non-fuel induced changes within the system: in air pre-heater leakage; in Forced Draft Fan bias effecting combustion air flow; in burner configurations; in fuel water content; and so forth. A method is needed in which such inter-dependencies are considered.
Complete thermodynamic understanding of fossil-fired thermal systems, for the purposes of improving heat rate and accuracy in regulatory reporting of data, requires the determination of fuel flow rate, fuel chemistry, fuel heating value, boiler efficiency, total effluent flow, emission rates of the common pollutants, and system heat rate. When determining these quantities, there is need to improve combustion stoichiometric consistency and thermodynamic conservations as affected by base inputs, including effluent concentrations, recognizing such inputs have inaccuracies.
There is no known art related to this invention. Although the technologies of ""711, ""853, ""956 and ""527 support this invention, they integrally employ effluent concentration measurements and other Operating Parameters, or their assumptions, whose technologies would benefit greatly, as would all Input/Loss methods, if such employments were systemically corrected in a manner as to assure combustion stoichiometric consistency and thermodynamic conservations of the thermal system.
This invention relates to a fossil-fired thermal system such as a power plant or steam generator, and, more particularly, to a method for determining correction factors to such a system""s Choice Operating Parameters such that combustion stoichiometric consistency and thermodynamic conservations are both achieved; corrected Choice Operating Parameters being then supplied to Input/Loss methods which may then be used to determine fuel flow, effluent flow, emission rates, fuel chemistry, fuel heating value, boiler efficiency, and/or system heat rate for on-line monitoring and improvement of the system.
This invention adds to the technology associated with Input/Loss methods. Specifically The Input/Loss Method has been applied through computer software, installable on a personal computer termed a xe2x80x9cCalculational Enginexe2x80x9d, and has been demonstrated as being highly useful to power plant engineers. The Calculational Engine receives data from the system""s data acquisition devices. The Calculational Engine""s software consists of the EX-FOSS, FUEL and HEATRATE programs described in ""711, and in FIG. 2 herein, and the ERR-CALC program described in FIG. 3 herein. ERR-CALC and HEATRATE now incorporate the teachings of this invention. The Calculational Engine continuously monitors system heat rate on-line, i.e., in essentially xe2x80x9creal-timexe2x80x9d, as long as the thermal system is burning fuel. The application of this invention to The Input/Loss Method as taught in ""711 and installed as part of the Calculational Engine significantly enhances the power plant engineer""s ability to improve system heat rate.
In applying its methodologies, this invention teaches the use of Method Options, System Options and Analysis Options whose selections by the user of this invention allow for a systematic approach to the determination and application of correction factors. These options help assure consistent stoichiometrics and thermodynamic conservations; they provide flexibility for the power plant engineer in selecting and correcting Choice Operating Parameters as some level of corrections will always be needed if computing fuel chemistry from Choice Operating Parameters.
Method Options relate to the specific numerical techniques used by ERR-CALC in determining correction factors to effluents and Operating Parameters to be optimized; all are used to obtain accurate fuel chemistry. System Options relate to how the Calculational Engine approaches system stoichiometrics in determining fuel chemistry and heating value, specifically it controls procedures in the HEATRATE program. Analysis Options relate to mechanistic computing techniques and specialized computations associated with the xe2x80x9cFuel Iterationsxe2x80x9d and the ERR-CALC program; e.g., at what frequency should effluent corrections be determined, how to process faulted conditions, and so forth.
The present invention provides a procedure for determining correction factors to a fossil-fired thermal system""s Choice Operating Parameters.
The present invention assures that changes in the values associated with a selection of Choice Operating Parameters impact system heat rate through System Effect Parameters, and not as individual and disconnected quantities; in other words, System Effect Parameters must be dependent on the selected Choice Operating Parameters.
The present invention, given a procedure for determining correction factors to Choice Operating Parameters, teaches how these factors may be applied using Method Options, System Options and Analysis Options developed for this invention.
Other advantages of the present invention will become apparent when its general methods are considered in conjunction with the accompanying drawings and the related inventions of ""711, ""853, ""956 and ""527.
This invention has been reduced to practice and installed for demonstration at a power plant to determine the operability and functionality of this invention. This demonstration has produced outstanding results.